Gizmodo reported early this week that Apple may be using software to perform additional automated checks on all new App Store submissions during the app review process.

Google Mobile lets you search the Web using your voice in a way that is technically off-limits to iPhone developers, according to a report.
Apple (App Store)

A series of tweets on Twitter from John Gruber of Daring Fireball and Craig Hockenberry of Iconfactory claimed that Apple is using an automated software tool that checks for private API calls in all new App Store submissions.

Hockenberry stated, "It wouldn't surprise me if the [App Store] review process now includes a step where they pass your binary through something that checks framework use."

Later, Gruber followed up with "I honestly don't know exactly what it flags. I have reason to believe that it is a serious tool, not simplistic."

The use of private APIs have always been prohibited by the iPhone SDK Developer Agreement because APIs may change or give third-party developers access to features that Apple does not want made publicly available. If this system exists, Apple might have found a way to quickly identify apps that use private APIs and reject them.

This also means that Apple may have the ability to check existing apps in the App Store that are known violators of Apple's policies such as Google Mobile for iPhone.